Many alternative solvents have been proposed to replace perchoroethylene. Liquid carbon dioxide is one example, but the high-pressure equipment needed for this inorganic solvent makes it unpractical and prohibitively expensive. A novel and more promising class of dry cleaning solvents are the so-called non-flammable, non-chlorine containing organic solvents. Examples may include hydrofluoroethers such as nonafluoromethoxybutane and nonafluoroethoxybutane or hydrofluorocarbons such as decafluoropentane. Hydrofluoroethers are relatively low in toxicity, are claimed to have zero ozone depletion potential, have relatively short atmospheric lifetimes, and can have very low global warming potentials relative to chloro fluorocarbons and many chloro fluorocarbon substitutes. Furthermore, HFEs are listed as non-volatile organic compounds by the EPA, and as such are not considered as smog precursors.
One of the main differences between a conventional aqueous washing process and a non-aqueous solvent based washing process is that the solvent has to be regenerated within the machine for reasons of costs, environment and convenience. The waste stream from a solvent based wash cycle has a complex composition and contains dissolved soils, particulate matter, detergent ingredients and water. To separate this broad spectrum of waste components from the solvent a number of efficient separation steps will be required. One of the most common separation steps used in commercial dry-cleaning operations is distillation or evaporation of the solvent which is very suitable to remove the majority of waste compounds. However, for in-home washing processes distillation has significant drawbacks due to safety requirements. An alternative separation method that would be capable to remove a broad spectrum of waste compounds is adsorption. The main drawback of this method is the generation of a significant amount of solid waste and the need for substantial consumer interaction which is not desired for reasons of safety and convenience. Another important constraint for a solvent reclamation system is that always sufficient cleaned solvent has to be present in the machine to start a new wash cycle. A slow reclamation rate could be compensated by a larger volume of solvent in the machine but this is not desired for reasons of costs and safety.
Considering the potential problems of industrial solvent cleaning systems if applied in the domestic environment, there is a need for a novel solvent reclamation method which gives a better rate of solvent reclamation whilst reducing the amount of waste, as compared with known processes. This problem is solved by the present invention which is aimed at providing a system for cleaning of solvent which is compatible with the conflicting requirements of process rate, required solvent quality, minimal consumer interaction, process safety and minimal environmental impact.
These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims which present, by way of illustration, various exemplary modes contemplated for carrying out the invention. The invention is capable of other different aspects and objects all without departing from the invention. For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Other than in the experimental examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”. Similarly, all percentages are weight/weight percentages of the total composition unless otherwise indicated. Numerical ranges expressed in the format “from x to y” are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format “from x to y” it is understood that all ranges combining the different endpoints are also contemplated. Where the term “comprising” is used in the specification or claims, it is not intended to exclude any terms, steps or features not specifically recited. All temperatures are in degrees Celsius (°C.) unless otherwise specified. All measurements are in SI units unless otherwise specified. All documents cited are in relevant part, incorporated herein by reference.